Bridges for Our Friends

Concrete can build bridges to sustainability in other ways.

This de facto wildlife crossing was not built as a deer pass. But even with all of the big rocks, animals still use it. Transportation engineers hope to encourage more safe wildlife crossings by incorporating science in bridge and highway designs.

Bass North is a wildlife crossing. Even though there are nice concrete sidewalks, the deer will not use them and will instead walk through the stream.

Additional business gained so far on traditional highway and street upgrades includes poured concrete sidewalks, pervious concrete bike paths, and precast-supported elevated crossovers. So as designers look beyond the right-of-ways, producers may want to look forward to opportunities for extra business.

Often an afterthought and supported by special federal spending bills, transportation designers are looking for more sustainable aspects to their projects. These opportunities encompass more than just material replacement. The EPA is leading this effort.

In February, EPA Administrator Lisa Jackson demonstrated the agency's support for greening the nation's highways. The EPA's 2011 budget proposal to the Senate Committee on Environment and Public Works includes a $5 million increase for Smart Growth work contained in the Healthy Communities Initiative.

The funding supports the Interagency Partnership for Sustainable Communities with the departments of Transportation and Housing and Urban Development. “The Smart Growth program works with federal partners and stakeholders to minimize the environmental impacts of development,” Jackson said.

One tangible indication of the interest was the call for papers for a new conference on green transportation by the American Society of Civil Engineers and the Transportation & Development Institute. The groups will host the event at the 2010 Green Streets & Highways Conference in November in Denver. Organizers feel the time is right to address the rapidly growing interest and activity in sustainable transportation. (To learn more, visit www.green-streets-highways.org.)

One of the more out-of-the box green concepts involving highway design focuses on the relationship between wildlife and vehicle traffic. At the PCI Conference in 2009, the sustainable construction session included a European perspective on how concrete construction benefits wildlife. “Using Pre-cast Concrete in Innovative Ecological Bridges Design and Construction,” authored by Marek Foglar, Jan Pencik, Vladimir Kristek and Radomir Bocek, outlined how ecological bridges and ecoducts mitigate negative aspects of transport infrastructure.

Ecoduct describes specially constructed overpasses for wildlife. Other designers have coined similar terms such as eco-bridge, wildlife bridge, green bridge, or wildlife overpass to describe bridges covered with natural vegetation. The largest are sometimes called landscape connectors while transportation designers in the U.S. and Canada use the term “wildlife crossings.”

Regardless of the term, these structures help eliminate habitat fragmentation and the loss of diversity of biotopes. The PCI presenters showed how innovative precast design and construction helped reduce the highway's influence on animals and saved human life and vehicular damage.

The focus on wildlife crossings is not just a European idea. Researchers in the U.S. and Canada have been looking for ways to protect drivers and animals.

Banff National Park

No other place in world contains as many different types of wildlife crossings as the Banff National Park in Alberta. Canada's oldest and perhaps most famous national park has the world's longest, yearround crossing monitoring program and the most data on wildlife's use of these safety corridors. The park's aggressive highway fencing program has reduced wildlife-vehicle collisions by more than 80% for elk and deer alone.

Park officials started the program when traffic increased in the early 1980s. They built the first crossing as they began to upgrade the 53-mile section of the Trans-Canada Highway that traverses the park in a two-lane and four-lane divided highway. More than halfway completed by last year, they have installed 22 wildlife underpasses and two wildlife overpasses along a 28-mile section of fence.

Sensitivity to wildlife and habitat challenges transportation agencies which are required to evaluate projects' impacts on endangered and threatened animal and plant species, and to consider resource conservation plans and inventories as part of planning. While progress has been made in developing methods to address project-specific impacts, a broader ecosystem approach to transportation project planning and development promises even greater benefits to wildlife and habitat while ensuring mobility for humans.

The National Cooperative Highway Research Program has sponsored the Evaluation of the Use and Effectiveness of Wildlife Crossings project. The team included nine ecologists and engineers and a web developer. Resources focused on ecological implications of roads and mitigation and the safety aspect of animal-vehicle collisions. The objective was to provide clearly written guidelines for selecting, configuring, and locating wildlife crossing structures, and monitoring and evaluating crossing effectiveness and maintenance of those structures.

The results are posted at AASHTO's Center for Environmental Excellence Web site at www.environment.trans portation.org under the Wildlife and Ecosystems' tab. It is an ideal place to learn the latest mitigation methods used in North America aimed at motorists and the animals they may encounter.

Greater emphasis

Transportation engineers have tried many methods and designs to lessen collisions with varying degrees of success. But with the added emphasis on environmental protection, these efforts have a higher priority. While many smaller animals do not threaten vehicles through collisions, they experience significant habitat loss and fragmentation because of roadway alignments. Transportation corridors limit wildlife's movement.

The report may help producers offer ideas during the design process about how concrete structures can help. Wildlife crossings may work well for one species but not for others. An international scan of wildlife habitat connectivity documented various strategies and designs used in Europe to improve the connectivity of wildlife habitats.

Developing successful designs, methods, and strategies to make roads safer for wildlife is just one aspect of managing highways to minimize the effects to the environment and maintain safety for motorists. The study also provided state DOTs with guidance on the use and effectiveness of wildlife crossings to mitigate habitat fragmentation and reduce the number of animal–vehicle collisions on our roads.